The present invention relates to an apparatus and method for cleaning containers, and especially glass or plastic sample containers for environmental testing. The invention more particularly relates to an automated and modular cleaning apparatus and method which consistently removes impurities from the interior surfaces of sample containers, and which at the same time greatly increases throughput, that is, the rate at which the sample containers can be processed.
Sample containers used in the environmental industry to perform chemical analysis must be thoroughly cleaned before reuse in order to meet rigorous standards of cleanliness set by the U.S. Environmental Protection Agency (EPA). Even low levels of impurities left on container surfaces after cleaning can invalidate test results performed on a sample, for example, a soil sample, which has been held in the container. To meet strict EPA cleanliness standards, sample containers have heretofore been cleaned manually. Each container is individually hand-scrubbed, usually in a non-phosphate detergent wash with tap water, and then hand-rinsed in a series of required solutions, typically in a rinsing sequence involving a nitric acid solution rinse, a deionized water rinse, and a solvent rinse, such as methylene chloride, for removing oils or grease. Manual washing processes are time intensive and often yield inconsistent results because of inattentive or fatigued workers who do not consistently swipe all the surfaces of every container.
In a known variation of the above-described manual cleaning approach, sample containers, instead of being washed by hand, are washed in a conventional industrial grade dishwasher, such as a Hobart brand washer, before they are manually processed through the required rinses. In a conventional dishwasher, a spinning spray arm beneath the inverted containers projects a wash solution and tap water rinse up into and about the containers to wash both inside and outside container surfaces. A relatively small portion of the spray emitted by the spinning spray arm actually reaches the inside of the container, and that portion that does strike the container's inside surfaces does so at low pressure and in an uncontrolled fashion. As a consequence, cleansing of the critical inside surfaces of the container tends to be incomplete and inconsistent in terms of removing impurities to required levels. A conventional washer is also a wasteful process, requiring large amounts of fluid to be emitted by the spin arm compared to the amount of fluid actually contacting the container surfaces.
U.S. Pat. No. 4,667,690 to Hartnig discloses yet another approach to washing containers, in this instance washing bottles prior to being filled by a filling machine with a liquid content such as, for example, a carbonated drink. In Hartnig, the bottles are processed on a continuous straight line conveyor system, rather than in a batch process. The rinsing cycle involves conveying the bottles in an inverted position over nozzles which are mounted on a rotating platform that is synchronized with the bottles. While this continuous process provides a more direct spray into the mouth of the inverted bottle, the spray still only reaches the inside surfaces of the bottle from a source outside the container. Thus, in Hartnig the spray is likely to reach only a portion of the interior surfaces of the container and the portions of the surfaces it does reach is reached at different angles and thus with varying degrees of effective scouring force. A cascade of fluid must be relied upon to clean a portion of the surfaces, and particularly shoulder surfaces near the neck of the container. Such limitations become particularly crucial when the cleanliness of the bottles must meet exacting EPA or similar standards.
The present invention is intended to overcome the disadvantages of existing approaches to cleansing sample containers and other types of containers. The invention improves over existing manual processes by greatly increasing throughput and providing consistent results. The invention also improves on the efficacy of existing automated and semi-automated approaches, whether involving batch or continuous processing, by providing a more direct, even, and consistent high pressure spray or fluid stream to the interior container surfaces to impart a more complete and thorough scouring action to these surfaces. The invention is uniquely adapted to handling a variety of container types and sizes, such as Boston round jars, amber wide mouth jars, round packers, cream jars, straight sided (paragon) jars, modern round (versus cylindrical round) plastic containers, and vials, and conserves fluids by efficiently directing sprays to surfaces to be cleaned in a focused manner. Finally, the invention provides for modular units that can flexibly be cascaded together to provide different cleaning, rinse and drying functions.